Chapters with parts should be ordered according to 'Order chapters by' value
Expected behaviour
When a chapter is added to a part, it should be ordered according to the current 'Order chapters by' value.
Current behaviour
This based on testing done a while back by @sidorelauku (see point 2 in #307 (comment 52002))
The ordering inside the part is based on which chapter we moved in firstly, the ordering is not updated automatically. To update the order user has to change the settings again to select A-Z so it applies again.
Steps to reproduce
@danjela please test this to confirm and update here.